The invention relates to small arms ammunition comprising a cartridge case adapted to contain a powder charge and having an open end, a closed end and a logitudinal axis, a percussion cap substantially centered at said closed end and a rotationally symmetric jacket bullet enclosing a metallic core located at said open end. The invention, also, relates to a jacket bullet of the kind just mentioned.
For clarification, the term "small arms" in this context relates to subcaliber arms having a caliber below 0.5 in (12.7 mm) and particularly to a caliber in the range of 0.17 to 0.25 in (4 to 6.35 mm).
A rotationally symmetric jacket bullet is known from a publication by the US Department of Commerce, National Technical Information Service, No. AD-A025 131 (Michael Pino, "The effect of varying certain parameters on the performance of the S.C.A.M.P. produced 5.56 mm projectile", DARCOM Intern Training Center, May 1976). The known bullet has an ogive-shaped profiled portion, a cylindrical central portion and a frustroconically-shaped rear portion. It is at first stated in the report (see page 3, para 2, lines 4 to 5) that "more specifically there is no published material on the effects of ogive, nose radius, or boattail, or spin rate". The profiled portion may be shaped parabolically, conically or spherically (1.c, page 24), however, said profiled portion is stated to require a change in rifle design if changed (see page 9, lines 2 to 4: "The ogive cannot be changed because of the effect of necessitating a complete redesign of the rifle.") Correspondingly the author of this report restricts himself to the effects produced by variations in the shape of the head and/or in the shape of the tail on the bullet performance.
In a paper presented at the International Symposium on Small Arms, Aberdeen, USA, in October 1979, by Beat Kneubuhl of the Armament Technology and Procurement Group, Ministry of Defense, Switzerland, the optimation of shapes for small arms bullets, in particular of the profiled portion in jacket bullets for small arms ammunition with respect to drag is reported. Starting point in the optimation is a mathematical formula developed by Haack for a projectile shape of minimum drag applicable to large-caliber projectiles having muzzle velocities in the supersonic range (Oerlikon Taschenbuch, Werkzeugmaschinenfabrik Oerlikon-Buhrle AG, Zurich, Schweiz, May 1981, Chapter 5.2.3., page 168 to 171). A parameter equation is derived therefrom for the calculation of an optimal shape with respect to drag for the profiled portion of the small arms bullet as mentioned.